On a Presumed Long-Lived Relaxed Radical Pair State in Closed Photosystem II

  • Theo A. Roelofs
  • Alfred R. Holzwarth


The concept of a long-lived relaxed radical pair (RRP) in closed photosystem (PS) II has been invoked to explain a prominent 11 ns lifetime component in the absorption decays of PS II particles (1). Radical pair (RP) states, with lifetimes between 4 and 36 ns and yields between 30%–60%, have been reported for several PS II preparations (2). Other groups reported a much shorter RP lifetime of 1–3 ns and a yield of only 10–20% (3–6), based on absorption, fluorescence and photovoltage kinetics. In contrast, a corresponding long-lived component in the fluorescence kinetics has never been carefully searched for. It is our aim to look for a potential long-lived fluorescence component in closed PS II that can be related to the charge recombination of the RRP, thus giving kinetic and energetic information on this presumed RRP state. The use of PS II particles is problematic because of the unevitable small fraction of disconnected Chi molecules, whose fluorescence kinetics interfere with that of a potential long-lived RRP recombination luminescence. For this reason we studied whole cells of green algae which contain fully intact PS II systems.


Radical Pair Relative Amplitude Fluorescence Component Fluorescence Kinetic Charge Separate State 
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Copyright information

© Springer Science+Business Media New York 1990

Authors and Affiliations

  • Theo A. Roelofs
    • 1
  • Alfred R. Holzwarth
    • 1
  1. 1.Max-Planck-Institut für StrahlenchemieMülheim a.d. RuhrGermany

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